Roll-on applicators are well known in the art. Usually, said applicators are containers comprising a hollow body for liquids, a ball and a retaining support means for said ball. These roll-on applicators generally allow to apply a liquid film from the inside of the hollow body to a selected surface. The common problem of these is to avoid leakage or spillage of the contained liquid during the periods of non-use of said roll-on applicators. The prior art solves this problem using the cooperation of a cap. Indeed, as disclosed in U.S. Pat. No. 3,036,328, U.S. Pat. No. 4,221,494, U.S. Pat. No. 4,221,495, U.S. Pat. No. 4,475,837 and U.S. Pat. No. 5,051,017, the ball is forced to engage and bear against a sealing surface of said retaining support means when the container is closed by the cap. But this solution to avoid leakage or spillage is inconvenient, if the above retaining support means with the ball is located under the level of the content. Indeed, leakage or spillage may occur during the operation of unscrewing the cap. For this reason, the roll-on applicator of the prior art usually has the retaining support means for the ball only on top of the corresponding container above the level of the content when said container is stored in its upright position.
Another disadvantage of the roll-on applicators of the prior art is given by the fact that the spread quantity cannot be increased. Instead, the prior art only teaches a decrease of said spread quantity. Indeed, the roll-on applicating means described in the above mentioned prior art can force the ball to engage and bear against a sealing surface of said retaining support means to decrease or stop completely the flow of the content on said ball. The inverse is never possible. On the contrary, an increased spread quantity is useful especially during pretreatment of stains on a fabric. Indeed, different stains may need a greater amount of liquid detergent for a more effective pretreatment. For example, stains made of certain constituents may need a greater quantity of detergent to get a more thorough and effective pretreatment. A greater quantity may also be needed to simply cover the dimension of the stain itself.
The above problems have been solved by the roll-on applicator described in the co-pending European patent application 94870179.2. Said roll-on applicator comprises a container adapted to contain and dispense a product. Said container comprises a hollow body, a dispensing opening, a ball and a flexible and resilient support means for said ball. Said flexible and resilient support means urges said ball against said dispensing opening, achieving a leak-tight engagement between said ball and said dispensing opening. Said flexible and resilient support means can be deformed in a resilient manner by an external force acting on said ball whereby said leak-tight engagement between said ball and said dispensing opening is disengaged, allowing said contained product to be spread by said ball. In practice, said flexible and resilient support means together with said ball acts as a valve which opens when pressing on said ball.
We found that said ball urged against said dispensing opening by said flexible and resilient support means achieves also a gas-tight engagement. In the following, "gas-tight engagement" means that no gases are able to pass through the engagement between the inside and the outside of the container. Alternatively, "gas-tight engagement" may also mean that the rate of pressure which may be released to the outside of the container through this engagement (hereinafter called "pressure release rate") is smaller than the rate of pressure produced inside said container. Therefore, a pressure builds up inside said container, because the amount of gases which are able to escape to the outside of said container is too small in respect to the pressure built up inside said container.
There are a number of possible factors which may lead to the existence of the pressure built up inside said container. The content of the package may, for example, be chemically unstable or may be subject to reaction with gases which may exist in the head space of the package, or alternatively, in certain specific circumstances, may react with the package material itself. Any chemical reactions involving the liquid contents may lead to production of gases, and hence to overpressure in the package.
Pressure built up inside said container may also occur when the temperature during the filling and sealing of the container is significantly different from external temperature during shipment, transportation and storage. Another possibility of a pressure difference may be caused by a different ambient pressure at the filling of the container from another ambient pressure at a different geographical location.
We found that the gas-tightness between said ball and said opening is further increased, or the pressure release rate is further reduced, when the pressure builds up inside said container. Indeed, this internal pressure further presses said ball against said dispensing opening further reducing the pressure release rate. The pressure release rate may be reduced down to almost no pressure release at all.
We further found that product can be expelled outwards when pressure has been built up inside said roll-on applicator described in the co-pending European patent application 94870179.2. To apply the contained product around the ball, it may be necessary to invert said container to convey said product towards said ball. This is not necessary, if said ball together with said flexible and resilient support means are always located under the filling level of said product. Nevertheless, in both cases, when pressing on said ball a free passage between said ball and said dispensing opening is created. Therefore, the built-up gas inside said container tends immediately to escape through said free passage, like a burp. Consequently, product situated between said built-up gas and said free passage may be also expelled in a rapid and an uncontrolled manner. This product rapidly expelled creates messiness and waste. Indeed, the expelled product may cover also other areas which were not intended to be covered by the user. Furthermore, the quantity of product expelled may be greater than necessary without the possibility of control.
It is therefore an object of the present invention to provide a leak-tight container comprising a roll-on applicator, but which nevertheless allows venting of gases to impede that product may be expelled from the inside of said container driven by the pressure built up inside the container, thereby avoiding messiness and waste of the contained product.